Why

This question starts with a deeplink 1mg://www.1mg.com/search.

package main  

import (  
    "fmt"  
    "net/url"  
    "runtime"  
)  

func main() {  
    fmt.Println(url.Parse("1mg://www.1mg.com/search"))  
    // <nil> parse "1mg://www.1mg.com/search": first path segment in URL cannot contain colon  
}

[Go Playground]

Is it a bug?

After I test some cases, I found that url.Parse doesn't limit the scheme of uri to http or https. It failed if the scheme starts with a digit.

Here is the comment for parsing scheme:

// Maybe rawURL is of the form scheme:path.
// (Scheme must be [a-zA-Z][a-zA-Z0-9+.-]*)
// If so, return scheme, path; else return "", rawURL.
func getScheme(rawURL string) (scheme, path string, err error) {
...

In the document of URI RFC 3986

scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )

It means that uri scheme implementation of golang fit the standard.