Still, if you follow that article I referred you to it may fix your issue - as 
the resolv.conf is auto-generated on OSX and includes hostname mappings.

> On Feb 22, 2021, at 11:48 PM, robert engels <reng...@ix.netcom.com> wrote:
> 
> It looks like the Go runtime implements its own DNS client on *unix platforms 
> including OSX.
> 
>> On Feb 22, 2021, at 11:40 PM, Peng Yu <pengyu...@gmail.com 
>> <mailto:pengyu...@gmail.com>> wrote:
>> 
>> I don’t understand why ping does not have the same problem. Ping is not 
>> based on C library?
>> 
>> On Mon, Feb 22, 2021 at 11:20 PM Ian Lance Taylor <i...@golang.org 
>> <mailto:i...@golang.org>> wrote:
>> On Mon, Feb 22, 2021 at 9:11 PM Peng Yu <pengyu...@gmail.com 
>> <mailto:pengyu...@gmail.com>> wrote:
>> >
>> > I tried 1.16.
>> >
>> > $ go version
>> > go version go1.16 darwin/amd64
>> >
>> > The problem still exists. When I change mymachine.local to
>> > mymachine_local, the problem is gone. So somehow, this is related to
>> > host resolution? It might try to DNS lookup the hostname, when it can
>> > not find it via DNS then it look up in /etc/hosts?
>> 
>> On Darwin I believe that by default we pass DNS lookups to the C
>> library.  So I think that what you are seeing is the behavior of the C
>> library.  Try setting the environment variable GODEBUG=netdns=go.
>> 
>> Ian
>> 
>> 
>> > On 2/22/21, Ian Lance Taylor <i...@golang.org <mailto:i...@golang.org>> 
>> > wrote:
>> > > On Mon, Feb 22, 2021 at 12:22 PM Peng Yu <pengyu...@gmail.com 
>> > > <mailto:pengyu...@gmail.com>> wrote:
>> > >>
>> > >> I run the following go program using net.Dial(). Depending on whether
>> > >> I specify a local hostname (defined in /etc/hosts) or an IP. I get
>> > >> very different runtimes.
>> > >>
>> > >> But `ping mymachine.local` resolves the hostname to an IP address
>> > >> instantaneously. So the two calls of the go program should have the
>> > >> same runtimes.
>> > >>
>> > >> Can anybody reproduce the same runtime problem? Does anybody know what
>> > >> is wrong with the implementation of net.Dial()? Thanks.
>> > >>
>> > >> $ ./main mymachine.local:22
>> > >> 2021/02/22 14:14:25 before
>> > >> 2021/02/22 14:14:30 after
>> > >> $ ./main 192.168.1.104:22 <http://192.168.1.104:22/>
>> > >> 2021/02/22 14:14:30 before
>> > >> 2021/02/22 14:14:30 after
>> > >> $ cat main.go
>> > >> package main
>> > >> import (
>> > >>   "net"
>> > >>   "log"
>> > >>   "os"
>> > >> )
>> > >>
>> > >> func main() {
>> > >>   dialAddr := os.Args[1]
>> > >>   log.Println("before")
>> > >>   _, err := net.Dial("tcp", dialAddr)
>> > >>   log.Println("after")
>> > >>   if err != nil {
>> > >>     log.Fatalln(err)
>> > >>   }
>> > >> }
>> > >
>> > > Which version of Go are you using?  What operating system are you running
>> > > on?
>> > >
>> > > It is possible that are running into https://golang.org/issue/35305 
>> > > <https://golang.org/issue/35305>,
>> > > which is fixed in 1.16.
>> > >
>> > > Ian
>> > >
>> >
>> >
>> > --
>> > Regards,
>> > Peng
>> -- 
>> Regards,
>> Peng
>> 
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