Specify key multiple times in values when providing a string slice

xrpc/xrpc.go

···
 	params := url.Values{}
 	for k, v := range p {
 		if s, ok := v.([]string); ok {
-			params.Add(k, strings.Join(s, ","))
+			for _, v := range s {
+				params.Add(k, v)
+			}
 		} else {
 			params.Add(k, fmt.Sprint(v))
 		}

xrpc/xrpc_test.go

···
 			input: map[string]interface{}{
 				"key": []string{"value1", "value2", "value3"},
 			},
-			expected: "key=value1%2Cvalue2%2Cvalue3",
+			expected: "key=value1&key=value2&key=value3",
 		},
 		{
 			name: "Mixed values",
···
 				"key1": "value1",
 				"key2": []string{"value2", "value3"},
 			},
-			expected: "key1=value1&key2=value2%2Cvalue3",
+			expected: "key1=value1&key2=value2&key2=value3",
 		},
 	}