How to check if error is tls handshake timeout in Go

Question

I have the following code making a request to URL and checking for errors.

import "net/http"

response, err := http.Head("url")

How do check if the error is due to tls handshake timeout? I tried the following:

if err != nil {
    tlsError, ok := err.(http.tlsHandshakeTimeoutError)
    if ok {
        // handle the error
    }
}

But I cannot access the http.tlsHandshakeTimeoutError type because it is unexported. How else can I check for the error type in go?

Answer 1

Yes tlsHandshakeTimeoutError - is not exported and the only one possibility to check on this error is:

import "net/url"

// ....

if urlError,ok :=  err.(*url.Error)  ; ok {
    if urlError.Error() == "net/http: TLS handshake timeout" {
        // handle the error
    }
}

Here is open ticket with discussion about it:

https://github.com/golang/go/issues/15935

By the way http errors (and tlsHandshakeTimeoutError also) provide also:

type WithTimeout interface {
   Timeout() bool
}

You can use it for you check if you don't like string comparsion. Here is example of isTemporary implementation from http2 package.