net: inconsistent dial tcp error message, some have colon, some don't

[digininja]

What version of Go are you using (go version)?

$ go version

$ go version
go version go1.16.2 linux/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/robin/.cache/go-build"
GOENV="/home/robin/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/robin/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/robin/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/go_current"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/go_current/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.2"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/xxxx/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2613921442=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Making HTTP requests and trying to handle errors

    client := &http.Client{
        CheckRedirect: func(req *http.Request, via []*http.Request) error {
            return http.ErrUseLastResponse
        },  
    }   

    log.Debugf("Requesting URL: %s\n", url)
    req, err := http.NewRequest("GET", url, nil)

    resp, err := client.Do(req)

  if err != nil {
        log.Debugf("Generic error: %s", err)
}

What did you expect to see?

Consistent use of the phrase dial tcp in error messages.

What did you see instead?

Some errors from dial tcp have a colon after the tcp, some don't:

DEBU[0003] Generic error: Get "http://host1.int": dial tcp 192.168.0.1:80: connect: no route to host

DEBU[0000] Generic error: Get "http://raasdfst.krynn.int": dial tcp: lookup host2.int on 192.168.0.2:53: no such host

Spotted this because I'm trying to tidy the errors up a bit to give a user a bit more information, my regexp was looking for dial tcp: then I found the one without the colon.

I've not dug in to see how may have or don't have the colon.

Thought I'd report it as it would be nice to have consistency over whether the colon is there or not.

[cherrymui]

cc @bradfitz