diff --git a/error.go b/error.go
index 83046a5..22a42b8 100644
--- a/error.go
+++ b/error.go
@@ -7,36 +7,27 @@ import (
 	"google.golang.org/grpc/codes"
 )
 
+var errMapping = map[int32]codes.Code{
+	http.StatusOK:                  codes.OK,
+	http.StatusBadRequest:          codes.InvalidArgument,
+	http.StatusRequestTimeout:      codes.DeadlineExceeded,
+	http.StatusNotFound:            codes.NotFound,
+	http.StatusConflict:            codes.AlreadyExists,
+	http.StatusForbidden:           codes.PermissionDenied,
+	http.StatusUnauthorized:        codes.Unauthenticated,
+	http.StatusPreconditionFailed:  codes.FailedPrecondition,
+	http.StatusNotImplemented:      codes.Unimplemented,
+	http.StatusInternalServerError: codes.Internal,
+	http.StatusServiceUnavailable:  codes.Unavailable,
+}
+
 func microError(err *errors.Error) codes.Code {
-	switch err {
-	case nil:
+	if err == nil {
 		return codes.OK
 	}
 
-	switch err.Code {
-	case http.StatusOK:
-		return codes.OK
-	case http.StatusBadRequest:
-		return codes.InvalidArgument
-	case http.StatusRequestTimeout:
-		return codes.DeadlineExceeded
-	case http.StatusNotFound:
-		return codes.NotFound
-	case http.StatusConflict:
-		return codes.AlreadyExists
-	case http.StatusForbidden:
-		return codes.PermissionDenied
-	case http.StatusUnauthorized:
-		return codes.Unauthenticated
-	case http.StatusPreconditionFailed:
-		return codes.FailedPrecondition
-	case http.StatusNotImplemented:
-		return codes.Unimplemented
-	case http.StatusInternalServerError:
-		return codes.Internal
-	case http.StatusServiceUnavailable:
-		return codes.Unavailable
+	if code, ok := errMapping[err.Code]; ok {
+		return code
 	}
-
 	return codes.Unknown
 }