check bin metadata first, require -bin be binary (technically breakin…

…g change)

js/modules/k6/grpc/client.go

@@ -459,19 +459,17 @@ func (c *Client) parseInvokeParams(paramsVal goja.Value) (*invokeParams, error)
 			}
 			for hk, kv := range rawHeaders {
 				// TODO(rogchap): Should we manage a string slice?
-				strval, ok := kv.(string)
-				if !ok {
-					// The spec defines that Binary-valued keys end in -bin
-					//  https://grpc.io/docs/what-is-grpc/core-concepts/#metadata
-					if strings.HasSuffix(hk, "-bin") {
-						binval, ok := kv.([]byte)
-						if !ok {
-							return result, fmt.Errorf("metadata %q value must be a string or binary", hk)
-						}
-						strval = string(binval)
-					} else {
-						return result, fmt.Errorf("metadata %q value must be a string", hk)
+				// The spec defines that Binary-valued keys end in -bin
+				//  https://grpc.io/docs/what-is-grpc/core-concepts/#metadata
+				var strval string
+				if strings.HasSuffix(hk, "-bin") {
+					binval, ok := kv.([]byte)
+					if !ok {
+						return result, fmt.Errorf("metadata %q value must be binary", hk)
 					}
+					strval = string(binval)
+				} else if strval, ok = kv.(string); !ok {
+					return result, fmt.Errorf("metadata %q value must be a string", hk)
 				}
 				result.Metadata[hk] = strval
 			}