code: func SignatureFromContext(ctx context.Context) *Signature {
  	if ctx == nil {
  		return nil
  	}
  
  	v := ctx.Value(signatureCtx)
  	if v == nil {
  		return nil
  	}
  
  	signature, _ := v.(*Signature)
  	return signature
  }
docs: // SignatureFromContext gets the signature from the context