complete fixup

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

http.go

@@ -116,13 +116,15 @@ func getErrors(service *protogen.Service) map[string]struct{} {
 }
 
 func generateServiceErrors(gfile *protogen.GeneratedFile, err *Error) {
+	gfile.P("// Code generated by protoc-gen-micro")
 	gfile.P("package ", err.packageName)
-	gfile.P("import (")
-	gfile.P(`"fmt"`)
-	gfile.P(")")
+	gfile.P()
+
+	gfile.Import(fmtPackage)
+
 	for _, typ := range err.types {
 		gfile.P("func (err *", typ[strings.LastIndex(typ, ".")+1:], ") Error() string {")
-		gfile.P(`return fmt.Sprintf("%#v", err)`)
+		gfile.P(`return `, fmtPackage.Ident("Sprintf"), `("%#v", err)`)
 		gfile.P("}")
 		gfile.P()
 	}