Add a new "utls" dialer type that uses the refraction-networking/utls
library to mimic browser TLS fingerprints (Chrome, Firefox, Safari, etc.).
- x/dialer/utls/dialer.go: Registered as "utls", mirrors the TLS dialer
with Handshake() using utls.UClient() for fingerprint emulation.
- x/dialer/utls/fingerprint.go: Maps string names (chrome, firefox, ios,
safari, edge, randomized, golang, custom) to utls.ClientHelloID presets.
- x/dialer/utls/metadata.go: Parses fingerprint from dialer metadata.
- go.mod: Add github.com/refraction-networking/utls v1.8.2.
The fingerprint is dialer-only metadata — the standard TLS dialer is
untouched. Falls back to crypto/tls if no fingerprint is configured.
Closesgo-gost/gost#31
ginuerzh