Get custom Data from TLS in G.

Example:

CustomInG[uint64]("goid")

Be careful!
Make sure your type and type name are correct.

YOU SHOULD CHECK THE SOURCE IN RUMTIME BEFORE USING.

https://cs.opensource.google/go/go/+/refs/heads/master:src/runtime/runtime2.go;drc=a031f4ef83edc132d5f49382bfef491161de2476;l=414