NewEchoJSONClient creates a JSON client that implements the Echo interface.

NewEchoProtobufClient creates a Protobuf client that implements the Echo interface.

WriteError writes an HTTP response with a valid Twirp error format.

EchoPathPrefix is used for all URL paths on a twirp Echo server.

HTTPClient is the interface used by generated clients to send HTTP requests.

TwirpServer is the interface generated server structs will support: they're HTTP handlers with additional methods for accessing metadata about the service.