NewRuntimeKey Register new runtime key @islog if the runtime key been logged and been transported @required is false , the runtime key will use the newValueFunc to generate a new value usage : trace_id newValueFunc : func() string { return uuid.New().String() }) to generate new trace_id p.s : the key should be lower case , because the grpc meta data will transfer all the key too lower case , if you use the upcase you will not find your runtime key in metadata.

RuntimeKey runtime key.