[Go] Add multiple file upload support (OpenAPITools#16956)

* add go echo api client github workflow

* add support for multi file upload in go client

* update go samples

.github/workflows/samples-go-client-echo-api.yaml

@@ -0,0 +1,32 @@
+name: Go Client (Echo API)
+
+on:
+  pull_request:
+    paths:
+      - samples/client/echo_api/go/**
+      - .github/workflows/samples-go-client-echo-api.yaml
+jobs:
+  build:
+    name: Test Go client
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sample:
+          # clients
+          - samples/client/echo_api/go
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v4
+        with:
+          go-version: "stable"
+      - name: Setup node.js
+        uses: actions/setup-node@v4
+      - name: Run echo server
+        run: |
+          git clone https://github.com/wing328/http-echo-server -b openapi-generator-test-server
+          (cd http-echo-server && npm install && npm start &)
+      - run: go version
+      - name: Run test
+        working-directory: ${{ matrix.sample }}
+        run: go test -mod=mod -v

modules/openapi-generator/src/main/resources/go/api.mustache

@@ -255,13 +255,32 @@ func (a *{{{classname}}}Service) {{nickname}}Execute(r {{#structPrefix}}{{&class
 {{/headerParams}}
 {{#formParams}}
 {{#isFile}}
+{{#isArray}}
 	var {{paramName}}LocalVarFormFileName string
 	var {{paramName}}LocalVarFileName     string
 	var {{paramName}}LocalVarFileBytes    []byte
 
-	{{paramName}}LocalVarFormFileName = "{{baseName}}"
+	{{paramName}}LocalVarFormFileName = "{{{baseName}}}"
+	{{paramName}}LocalVarFile := r.{{paramName}}
 
+	if {{paramName}}LocalVarFile != nil {
+		// loop through the array to prepare multiple files upload
+		for _, {{paramName}}LocalVarFileValue := range {{paramName}}LocalVarFile {
+			fbs, _ := io.ReadAll({{paramName}}LocalVarFileValue)
+
+			{{paramName}}LocalVarFileBytes = fbs
+			{{paramName}}LocalVarFileName = {{paramName}}LocalVarFileValue.Name()
+			{{paramName}}LocalVarFileValue.Close()
+			formFiles = append(formFiles, formFile{fileBytes: {{paramName}}LocalVarFileBytes, fileName: {{paramName}}LocalVarFileName, formFileName: {{paramName}}LocalVarFormFileName})
+		}
+	}
+{{/isArray}}
+{{^isArray}}
+	var {{paramName}}LocalVarFormFileName string
+	var {{paramName}}LocalVarFileName     string
+	var {{paramName}}LocalVarFileBytes    []byte
 
+	{{paramName}}LocalVarFormFileName = "{{{baseName}}}"
 	{{paramName}}LocalVarFile := r.{{paramName}}
 
 	if {{paramName}}LocalVarFile != nil {
@@ -272,6 +291,7 @@ func (a *{{{classname}}}Service) {{nickname}}Execute(r {{#structPrefix}}{{&class
 		{{paramName}}LocalVarFile.Close()
 		formFiles = append(formFiles, formFile{fileBytes: {{paramName}}LocalVarFileBytes, fileName: {{paramName}}LocalVarFileName, formFileName: {{paramName}}LocalVarFormFileName})
 	}
+{{/isArray}}
 {{/isFile}}
 {{^isFile}}
 {{#required}}