THRIFT-5240: Tweak the default go server connectivity check interval

Client: go

Because of the Go runtime bug [1], the previous default value of 1ms is
not a great default as it could cause excessive cpu usage. Use 5ms
instead as a balance between being useful and not causing too much cpu
overhead.

It's still configurable.

[1]: golang/go#27707

lib/go/README.md

@@ -107,4 +107,9 @@ main function:
 
     thrift.ServerConnectivityCheckInterval = 0
 
+Please be advised that due to a
+[Go runtime bug](https://github.com/golang/go/issues/27707), currently
+if this interval is set to a value too low (for example, 1ms), it might cause
+excessive cpu overhead.
+
 This feature is also only enabled on non-oneway endpoints.

lib/go/thrift/simple_server.go

@@ -46,7 +46,7 @@ var ErrAbandonRequest = errors.New("request abandoned")
 // implementations can change its value to control the behavior.
 //
 // If it's changed to <=0, the feature will be disabled.
-var ServerConnectivityCheckInterval = time.Millisecond
+var ServerConnectivityCheckInterval = time.Millisecond * 5
 
 /*
  * This is not a typical TSimpleServer as it is not blocked after accept a socket.