server.go
func (ctx *RequestCtx) TLSConnectionState() *tls.ConnectionState {
	tlsConn, ok := ctx.c.(connTLSer)
	if !ok {
		return nil
	}
	state := tlsConn.ConnectionState()
	return &state
}
func (ctx *RequestCtx) TLSConnectionState() *tls.ConnectionState {
	tlsConn, ok := ctx.c.(connTLSer)
	if !ok {
		return nil
	}
	state := tlsConn.ConnectionState()
	return &state
}
// TLSConnectionState returns TLS connection state.
//
// The function returns nil if the underlying connection isn't tls.Conn.
//
// The returned state may be used for verifying TLS version, client certificates,
// etc.