diff --git a/go/tools/builders/generate_test_main.go b/go/tools/builders/generate_test_main.go
index 4cc23e0471..ff150249a9 100644
--- a/go/tools/builders/generate_test_main.go
+++ b/go/tools/builders/generate_test_main.go
@@ -58,6 +58,7 @@ import (
 	"log"
 	"os"
 	"fmt"
+	"strconv"
 	"testing"
 	"testing/internal/testdeps"
 
@@ -72,7 +73,7 @@ import (
 {{end}}
 )
 
-var tests = []testing.InternalTest{
+var allTests = []testing.InternalTest{
 {{range .TestNames}}
 	{"{{.}}", undertest.{{.}} },
 {{end}}
@@ -84,6 +85,24 @@ var benchmarks = []testing.InternalBenchmark{
 {{end}}
 }
 
+func testsInShard() []testing.InternalTest {
+	totalShards, err := strconv.Atoi(os.Getenv("TEST_TOTAL_SHARDS"))
+	if err != nil || totalShards <= 1 {
+		return allTests
+	}
+	shardIndex, err := strconv.Atoi(os.Getenv("TEST_SHARD_INDEX"))
+	if err != nil || shardIndex < 0 {
+		return allTests
+	}
+	tests := []testing.InternalTest{}
+	for i, t := range allTests {
+		if i % totalShards == shardIndex {
+			tests = append(tests, t)
+		}
+	}
+	return tests
+}
+
 func coverRegisterAll() testing.Cover {
 	coverage := testing.Cover{
 		Mode: "set",
@@ -144,7 +163,7 @@ func main() {
 		testing.RegisterCover(coverage)
 	}
 
-	m := testing.MainStart(testdeps.TestDeps{}, tests, benchmarks, nil)
+	m := testing.MainStart(testdeps.TestDeps{}, testsInShard(), benchmarks, nil)
 	{{if not .HasTestMain}}
 	os.Exit(m.Run())
 	{{else}}