v5.8.1 release notes

• Better IPv6 support:
  • Fixed an error when starting the server when server.host was an IPv6.
  • server.Host(), server.BaseURL() and server.ProxyBaseURL() properly format IPv6 hosts with enclosing square brackets, which also fixes route.BuildURL() and route.BuildProxyURL() when the host is an IPv6.
  • server.BaseURL() now converts :: to ::1 (IPv6 loopback).