2.6.66

• Fix #2182: Be more flexible in which commands are "primary only" in order to support users with replicas that are explicitly configured to allow writes (#2183 by @slorello89)
• Adds: IConnectionMultiplexer now implements IAsyncDisposable (#2161 by @kimsey0)
• Adds: IConnectionMultiplexer.GetServers() to get all IServer instances for a multiplexer (#2203 by @NickCraver)
• Fix #2016: Align server selection with supported commands (e.g. with writable servers) to reduce Command cannot be issued to a replica errors (#2191 by @slorello89)
• Performance: Optimization around timeout processing to reduce lock contention in the case of many items that haven't yet timed out during a heartbeat (#2217 by @NickCraver)
• Fix #2223: Resolve sync-context issues (missing ConfigureAwait(false)) (#2229 by @mgravell)
• Fix #1968: Improved handling of EVAL scripts during server restarts and failovers, detecting and re-sending the script for a retry when needed (#2170 by @martintmk)
• Adds: ConfigurationOptions.SslClientAuthenticationOptions (netcoreapp3.1/net5.0+ only) to give more control over SSL/TLS authentication (#2224 by @NickCraver)
• Fix #2240: Improve support for DNS-based IPv6 endpoints (#2241 by @NickCraver)
• Adds: ConfigurationOptions.HeartbeatInterval (Advanced Setting - see docs) To allow more finite control of the client heartbeat, which encompases how often command timeouts are actually evaluated - still defaults to 1,000 ms (#2243 by @NickCraver)
• Fix #1879: Improve exception message when the wrong password is used (#2246 by @NickCraver)
• Fix #2233: Repeated connection to Sentinel servers using the same ConfigurationOptions would fail (#2242 by @NickCraver)