GRPC_ARG_MAX_CONCURRENT_STREAMS

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
extern (C)
static if(!is(typeof(GRPC_ARG_MAX_CONCURRENT_STREAMS)))
enum GRPC_ARG_MAX_CONCURRENT_STREAMS = "grpc.max_concurrent_streams";

Meta