Adding the Program.cs file to each module was the issue.

booking-modular-monolith-sample.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.30114.105
+# Visual Studio Version 17
+VisualStudioVersion = 17.8.34309.116
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Api", "Api", "{F7A6067F-42D3-4F59-BC88-0A57A4B903F1}"
 EndProject
@@ -11,7 +11,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Modules", "Modules", "{34A7
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{CA40C0D9-091C-4098-8F0E-FEA1C777303E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BuildingBlocks", "src\BuildingBlocks\BuildingBlocks.csproj", "{285E55A8-0C26-41DB-AD72-0D0557BDAE76}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "BuildingBlocks", "src\BuildingBlocks\BuildingBlocks.csproj", "{285E55A8-0C26-41DB-AD72-0D0557BDAE76}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Booking", "Booking", "{F8725F12-8D95-4A62-9D27-84909E215D36}"
 EndProject
@@ -29,41 +29,29 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{70395541-D3C
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{0468D5FF-FA73-422F-AB68-A3900B0DB937}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Flight", "src\Modules\Flight\src\Flight\Flight.csproj", "{56CE1785-AA9B-427E-AE29-492A637DDD1A}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Flight", "src\Modules\Flight\src\Flight\Flight.csproj", "{56CE1785-AA9B-427E-AE29-492A637DDD1A}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Identity", "src\Modules\Identity\src\Identity\Identity.csproj", "{7A590034-D985-4BC6-82ED-83839AAB052D}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Identity", "src\Modules\Identity\src\Identity\Identity.csproj", "{7A590034-D985-4BC6-82ED-83839AAB052D}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Passenger", "src\Modules\Passenger\src\Passenger\Passenger.csproj", "{747845A0-25C5-4E01-A735-1B1E2ADA9554}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Passenger", "src\Modules\Passenger\src\Passenger\Passenger.csproj", "{747845A0-25C5-4E01-A735-1B1E2ADA9554}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Booking", "src\Modules\Booking\src\Booking\Booking.csproj", "{E534AFC5-DC20-479F-8AC1-86CD28ABA682}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Booking", "src\Modules\Booking\src\Booking\Booking.csproj", "{E534AFC5-DC20-479F-8AC1-86CD28ABA682}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Api", "src\Api\src\Api.csproj", "{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Api", "src\Api\src\Api.csproj", "{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Booking.Api", "src\Modules\Booking\src\Booking.Api\Booking.Api.csproj", "{BB3B9761-FA12-47A0-B630-35F5FCAF5A93}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Identity.Api", "src\Modules\Identity\src\Identity.Api\Identity.Api.csproj", "{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Flight.Api", "src\Modules\Flight\src\Flight.Api\Flight.Api.csproj", "{3AE5F6C4-D2D3-4564-84AF-DC773A85083E}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Passenger.Api", "src\Modules\Passenger\src\Passenger.Api\Passenger.Api.csproj", "{13A85C52-7AC7-4AE9-BDF6-96611B269EC6}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
 		Release|Any CPU = Release|Any CPU
 	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
-	EndGlobalSection
-	GlobalSection(NestedProjects) = preSolution
-		{CA40C0D9-091C-4098-8F0E-FEA1C777303E} = {F7A6067F-42D3-4F59-BC88-0A57A4B903F1}
-		{285E55A8-0C26-41DB-AD72-0D0557BDAE76} = {BD4BC863-4353-4CDF-8085-F0212A2EEA11}
-		{F8725F12-8D95-4A62-9D27-84909E215D36} = {34A73111-C432-4051-ACE5-968F7ED3F634}
-		{4A86BE62-83F4-4CB6-94F8-A5F00304A44E} = {34A73111-C432-4051-ACE5-968F7ED3F634}
-		{CB89FC18-7C55-4671-A4D6-025FF54C2741} = {34A73111-C432-4051-ACE5-968F7ED3F634}
-		{E5653FEF-8BC9-4B78-AF78-10BA09A06462} = {34A73111-C432-4051-ACE5-968F7ED3F634}
-		{BAB888BA-2703-4114-93C2-501EA48454E4} = {F8725F12-8D95-4A62-9D27-84909E215D36}
-		{2BF6ABC1-6F8C-4FE2-97DB-862669F3913F} = {4A86BE62-83F4-4CB6-94F8-A5F00304A44E}
-		{70395541-D3C0-4E8B-830F-E1C93926F9C8} = {CB89FC18-7C55-4671-A4D6-025FF54C2741}
-		{0468D5FF-FA73-422F-AB68-A3900B0DB937} = {E5653FEF-8BC9-4B78-AF78-10BA09A06462}
-		{56CE1785-AA9B-427E-AE29-492A637DDD1A} = {2BF6ABC1-6F8C-4FE2-97DB-862669F3913F}
-		{7A590034-D985-4BC6-82ED-83839AAB052D} = {70395541-D3C0-4E8B-830F-E1C93926F9C8}
-		{747845A0-25C5-4E01-A735-1B1E2ADA9554} = {0468D5FF-FA73-422F-AB68-A3900B0DB937}
-		{E534AFC5-DC20-479F-8AC1-86CD28ABA682} = {BAB888BA-2703-4114-93C2-501EA48454E4}
-		{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4} = {CA40C0D9-091C-4098-8F0E-FEA1C777303E}
-	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{285E55A8-0C26-41DB-AD72-0D0557BDAE76}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{285E55A8-0C26-41DB-AD72-0D0557BDAE76}.Debug|Any CPU.Build.0 = Debug|Any CPU
@@ -89,5 +77,48 @@ Global
 		{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4}.Release|Any CPU.Build.0 = Release|Any CPU
+		{BB3B9761-FA12-47A0-B630-35F5FCAF5A93}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{BB3B9761-FA12-47A0-B630-35F5FCAF5A93}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{BB3B9761-FA12-47A0-B630-35F5FCAF5A93}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{BB3B9761-FA12-47A0-B630-35F5FCAF5A93}.Release|Any CPU.Build.0 = Release|Any CPU
+		{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3AE5F6C4-D2D3-4564-84AF-DC773A85083E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3AE5F6C4-D2D3-4564-84AF-DC773A85083E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3AE5F6C4-D2D3-4564-84AF-DC773A85083E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3AE5F6C4-D2D3-4564-84AF-DC773A85083E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{13A85C52-7AC7-4AE9-BDF6-96611B269EC6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{13A85C52-7AC7-4AE9-BDF6-96611B269EC6}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{13A85C52-7AC7-4AE9-BDF6-96611B269EC6}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{13A85C52-7AC7-4AE9-BDF6-96611B269EC6}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(NestedProjects) = preSolution
+		{CA40C0D9-091C-4098-8F0E-FEA1C777303E} = {F7A6067F-42D3-4F59-BC88-0A57A4B903F1}
+		{285E55A8-0C26-41DB-AD72-0D0557BDAE76} = {BD4BC863-4353-4CDF-8085-F0212A2EEA11}
+		{F8725F12-8D95-4A62-9D27-84909E215D36} = {34A73111-C432-4051-ACE5-968F7ED3F634}
+		{4A86BE62-83F4-4CB6-94F8-A5F00304A44E} = {34A73111-C432-4051-ACE5-968F7ED3F634}
+		{CB89FC18-7C55-4671-A4D6-025FF54C2741} = {34A73111-C432-4051-ACE5-968F7ED3F634}
+		{E5653FEF-8BC9-4B78-AF78-10BA09A06462} = {34A73111-C432-4051-ACE5-968F7ED3F634}
+		{BAB888BA-2703-4114-93C2-501EA48454E4} = {F8725F12-8D95-4A62-9D27-84909E215D36}
+		{2BF6ABC1-6F8C-4FE2-97DB-862669F3913F} = {4A86BE62-83F4-4CB6-94F8-A5F00304A44E}
+		{70395541-D3C0-4E8B-830F-E1C93926F9C8} = {CB89FC18-7C55-4671-A4D6-025FF54C2741}
+		{0468D5FF-FA73-422F-AB68-A3900B0DB937} = {E5653FEF-8BC9-4B78-AF78-10BA09A06462}
+		{56CE1785-AA9B-427E-AE29-492A637DDD1A} = {2BF6ABC1-6F8C-4FE2-97DB-862669F3913F}
+		{7A590034-D985-4BC6-82ED-83839AAB052D} = {70395541-D3C0-4E8B-830F-E1C93926F9C8}
+		{747845A0-25C5-4E01-A735-1B1E2ADA9554} = {0468D5FF-FA73-422F-AB68-A3900B0DB937}
+		{E534AFC5-DC20-479F-8AC1-86CD28ABA682} = {BAB888BA-2703-4114-93C2-501EA48454E4}
+		{3B2CDE51-E7F9-418E-AA28-4BFD86C728F4} = {CA40C0D9-091C-4098-8F0E-FEA1C777303E}
+		{BB3B9761-FA12-47A0-B630-35F5FCAF5A93} = {BAB888BA-2703-4114-93C2-501EA48454E4}
+		{55E5C66B-FC0C-4B5B-A0F3-A4DF13172656} = {70395541-D3C0-4E8B-830F-E1C93926F9C8}
+		{3AE5F6C4-D2D3-4564-84AF-DC773A85083E} = {2BF6ABC1-6F8C-4FE2-97DB-862669F3913F}
+		{13A85C52-7AC7-4AE9-BDF6-96611B269EC6} = {0468D5FF-FA73-422F-AB68-A3900B0DB937}
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {A809DAA3-8F41-4B78-8F09-F03B2FB31AB5}
 	EndGlobalSection
 EndGlobal

src/Modules/Booking/src/Booking.Api/Booking.Api.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.4.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Booking\Booking.csproj" />
+  </ItemGroup>
+
+</Project>

src/Modules/Booking/src/Booking.Api/Program.cs

@@ -0,0 +1,67 @@
+using Booking;
+using BuildingBlocks.CAP;
+using BuildingBlocks.Domain;
+using BuildingBlocks.Exception;
+using BuildingBlocks.Jwt;
+using BuildingBlocks.Logging;
+using BuildingBlocks.MediatR;
+using BuildingBlocks.Swagger;
+using BuildingBlocks.Web;
+using Figgle;
+using Hellang.Middleware.ProblemDetails;
+using Microsoft.AspNetCore.Mvc.ApiExplorer;
+using Serilog;
+
+var builder = WebApplication.CreateBuilder(args);
+var configuration = builder.Configuration;
+var env = builder.Environment;
+
+var appOptions = builder.Services.GetOptions<AppOptions>("AppOptions");
+Console.WriteLine(FiggleFonts.Standard.Render(appOptions.Name));
+
+builder.AddCustomSerilog(env);
+builder.Services.AddJwt();
+builder.Services.AddControllers();
+builder.Services.AddHttpContextAccessor();
+
+builder.Services.AddCustomCap();
+builder.Services.AddTransient<IBusPublisher, BusPublisher>();
+builder.Services.AddCustomVersioning();
+
+builder.Services.AddCustomSwagger(configuration,
+    typeof(BookingRoot).Assembly);
+
+builder.Services.AddCustomProblemDetails();
+
+builder.Services.AddBookingModules(configuration);
+
+builder.Services.AddEasyCaching(options => { options.UseInMemory(configuration, "mem"); });
+
+builder.Services.AddCustomMediatR(
+    typeof(BookingRoot).Assembly
+);
+
+var app = builder.Build();
+
+if (app.Environment.IsDevelopment())
+{
+    var provider = app.Services.GetService<IApiVersionDescriptionProvider>();
+    app.UseCustomSwagger(provider);
+}
+
+app.UseSerilogRequestLogging();
+app.UseCorrelationId();
+app.UseRouting();
+app.UseAuthentication();
+app.UseAuthorization();
+app.UseHttpsRedirection();
+
+app.UseBookingModules();
+
+app.UseProblemDetails();
+
+app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
+
+app.MapGet("/", x => x.Response.WriteAsync(appOptions.Name));
+
+app.Run();

src/Modules/Booking/src/Booking.Api/Properties/launchSettings.json

@@ -0,0 +1,41 @@
+{
+  "$schema": "http://json.schemastore.org/launchsettings.json",
+  "iisSettings": {
+    "windowsAuthentication": false,
+    "anonymousAuthentication": true,
+    "iisExpress": {
+      "applicationUrl": "http://localhost:62393",
+      "sslPort": 44326
+    }
+  },
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "launchUrl": "swagger",
+      "applicationUrl": "http://localhost:5156",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "launchUrl": "swagger",
+      "applicationUrl": "https://localhost:7195;http://localhost:5156",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "IIS Express": {
+      "commandName": "IISExpress",
+      "launchBrowser": true,
+      "launchUrl": "swagger",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

src/Modules/Booking/src/Booking.Api/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

src/Modules/Booking/src/Booking.Api/appsettings.json

@@ -0,0 +1,43 @@
+{
+  "AppOptions": {
+    "Name": "Booking-Modular-Monolith"
+  },
+  "LogOptions": {
+    "Level": "information",
+    "LogTemplate": "{Timestamp:HH:mm:ss} [{Level:u4}] {Message:lj}{NewLine}{Exception}",
+    "Elastic": {
+      "Enabled": true,
+      "ElasticServiceUrl": "http://localhost:9200"
+    },
+    "File": {
+      "Enabled": false,
+      "Path": "logs/logs.txt",
+      "Interval": "day"
+    },
+    "Sentry": {
+      "Enabled": false,
+      "Dsn": "",
+      "MinimumBreadcrumbLevel": "information",
+      "MinimumEventLevel": "error"
+    }
+  },
+  "ConnectionStrings": {
+    "Booking": "Server=.\\sqlexpress;Database=BookingDB-Monolith;Trusted_Connection=True;MultipleActiveResultSets=true"
+  },
+  "Jwt": {
+    "Authority": "https://localhost:5000",
+    "Audience": "booking"
+  },
+  "Grpc": {
+    "FlightAddress": "https://localhost:5000",
+    "PassengerAddress": "https://localhost:5000"
+  },
+  "EventStore": {
+    "ConnectionString": "esdb://localhost:2113?tls=false"
+  },
+  "PersistMessageOptions": {
+    "Interval": 30,
+    "Enabled": true
+  },
+  "AllowedHosts": "*"
+}

src/Modules/Flight/src/Flight.Api/Flight.Api.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.4.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Flight\Flight.csproj" />
+  </ItemGroup>
+
+</Project>

src/Modules/Flight/src/Flight.Api/Program.cs

@@ -0,0 +1,67 @@
+using BuildingBlocks.CAP;
+using BuildingBlocks.Domain;
+using BuildingBlocks.Exception;
+using BuildingBlocks.Jwt;
+using BuildingBlocks.Logging;
+using BuildingBlocks.MediatR;
+using BuildingBlocks.Swagger;
+using BuildingBlocks.Web;
+using Figgle;
+using Flight;
+using Hellang.Middleware.ProblemDetails;
+using Microsoft.AspNetCore.Mvc.ApiExplorer;
+using Serilog;
+
+var builder = WebApplication.CreateBuilder(args);
+var configuration = builder.Configuration;
+var env = builder.Environment;
+
+var appOptions = builder.Services.GetOptions<AppOptions>("AppOptions");
+Console.WriteLine(FiggleFonts.Standard.Render(appOptions.Name));
+
+builder.AddCustomSerilog(env);
+builder.Services.AddJwt();
+builder.Services.AddControllers();
+builder.Services.AddHttpContextAccessor();
+
+builder.Services.AddCustomCap();
+builder.Services.AddTransient<IBusPublisher, BusPublisher>();
+builder.Services.AddCustomVersioning();
+
+builder.Services.AddCustomSwagger(configuration,
+    typeof(FlightRoot).Assembly);
+
+builder.Services.AddCustomProblemDetails();
+
+builder.Services.AddFlightModules(configuration);
+
+builder.Services.AddEasyCaching(options => { options.UseInMemory(configuration, "mem"); });
+
+builder.Services.AddCustomMediatR(
+    typeof(FlightRoot).Assembly
+);
+
+var app = builder.Build();
+
+if (app.Environment.IsDevelopment())
+{
+    var provider = app.Services.GetService<IApiVersionDescriptionProvider>();
+    app.UseCustomSwagger(provider);
+}
+
+app.UseSerilogRequestLogging();
+app.UseCorrelationId();
+app.UseRouting();
+app.UseAuthentication();
+app.UseAuthorization();
+app.UseHttpsRedirection();
+
+app.UseFlightModules();
+
+app.UseProblemDetails();
+
+app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
+
+app.MapGet("/", x => x.Response.WriteAsync(appOptions.Name));
+
+app.Run();