Go: Output setup-go compatible pre-release identifiers

Author: mbg

go/extractor/util/semver.go

@@ -132,5 +132,10 @@ func (ver semVer) MajorMinor() SemVer {
 }
 
 func (ver semVer) StandardSemVer() string {
-	return string(ver)[1:]
+	// Drop the 'v' prefix from the version string.
+	result := string(ver)[1:]
+
+	// Correct the pre-release identifier for use with `setup-go`, if one is present.
+	// This still remains a standard semantic version.
+	return strings.Replace(result, "-rc", "-rc.", 1)
 }

go/extractor/util/semver_test.go

@@ -1,6 +1,7 @@
 package util
 
 import (
+	"strings"
 	"testing"
 
 	"golang.org/x/mod/semver"
@@ -52,6 +53,8 @@ func TestNewSemVer(t *testing.T) {
 						result,
 					)
 				}
+
+				expected = strings.Replace(expected, "-rc1", "-rc.1", 1)
 				if result.StandardSemVer() != expected[1:] {
 					t.Errorf(
 						"Expected NewSemVer(\"%s\").StandardSemVer() to return \"%s\", but got \"%s\".",