cmd/protoc-gen-go: add protoc suffix

Change-Id: Ib09bd3cbd15088d534de34b08d01a4d7a4880c0a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/306209
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Damien Neil <dneil@google.com>
Trust: Joe Tsai <thebrokentoaster@gmail.com>
Trust: Damien Neil <dneil@google.com>
diff --git a/cmd/protoc-gen-go/internal_gengo/main.go b/cmd/protoc-gen-go/internal_gengo/main.go
index 2c74041..675488a 100644
--- a/cmd/protoc-gen-go/internal_gengo/main.go
+++ b/cmd/protoc-gen-go/internal_gengo/main.go
@@ -128,6 +128,9 @@
 		protocVersion := "(unknown)"
 		if v := gen.Request.GetCompilerVersion(); v != nil {
 			protocVersion = fmt.Sprintf("v%v.%v.%v", v.GetMajor(), v.GetMinor(), v.GetPatch())
+			if s := v.GetSuffix(); s != "" {
+				protocVersion += "-" + s
+			}
 		}
 		g.P("// \tprotoc-gen-go ", protocGenGoVersion)
 		g.P("// \tprotoc        ", protocVersion)