all: drop support for Go 1.16 and Go 1.17

src/testing/testing.go

@@ -511,3 +511,15 @@ type InternalExample struct {
 	Output    string
 	Unordered bool
 }
+
+// MainStart is meant for use by tests generated by 'go test'.
+// It is not meant to be called directly and is not subject to the Go 1 compatibility document.
+// It may change signature from release to release.
+func MainStart(deps interface{}, tests []InternalTest, benchmarks []InternalBenchmark, fuzzTargets []InternalFuzzTarget, examples []InternalExample) *M {
+	Init()
+	return &M{
+		Tests:      tests,
+		Benchmarks: benchmarks,
+		deps:       deps.(testDeps),
+	}
+}

src/testing/testing_go118.go

@@ -1,16 +0,0 @@
-//go:build go1.18
-// +build go1.18
-
-package testing
-
-// MainStart is meant for use by tests generated by 'go test'.
-// It is not meant to be called directly and is not subject to the Go 1 compatibility document.
-// It may change signature from release to release.
-func MainStart(deps interface{}, tests []InternalTest, benchmarks []InternalBenchmark, fuzzTargets []InternalFuzzTarget, examples []InternalExample) *M {
-	Init()
-	return &M{
-		Tests:      tests,
-		Benchmarks: benchmarks,
-		deps:       deps.(testDeps),
-	}
-}

src/testing/testing_other.go

@@ -1,16 +0,0 @@
-//go:build !go1.18
-// +build !go1.18
-
-package testing
-
-// MainStart is meant for use by tests generated by 'go test'.
-// It is not meant to be called directly and is not subject to the Go 1 compatibility document.
-// It may change signature from release to release.
-func MainStart(deps interface{}, tests []InternalTest, benchmarks []InternalBenchmark, examples []InternalExample) *M {
-	Init()
-	return &M{
-		Tests:      tests,
-		Benchmarks: benchmarks,
-		deps:       deps.(testDeps),
-	}
-}