multi: fix a-vs-an typos

routing/errors.go

@@ -61,7 +61,7 @@ func (e *routerError) Error() string {
 // A compile time check to ensure routerError implements the error interface.
 var _ error = (*routerError)(nil)
 
-// newErr creates an routerError by the given error description and its
+// newErr creates a routerError by the given error description and its
 // corresponding error code.
 func newErr(code errorCode, a interface{}) *routerError {
 	return &routerError{
@@ -70,7 +70,7 @@ func newErr(code errorCode, a interface{}) *routerError {
 	}
 }
 
-// newErrf creates an routerError by the given error formatted description and
+// newErrf creates a routerError by the given error formatted description and
 // its corresponding error code.
 func newErrf(code errorCode, format string, a ...interface{}) *routerError {
 	return &routerError{