Fix "Usage" code in Readme

[TAbdiukov]

Description

The example code in README.md in incorrect (and probably outdated). This PR fixes this.

Change can be viewed here: 7c7cc2c

p := proxy.NewProvider("").Get("https", "https://rapid7.com")

is changed to,

p := proxy.NewProvider("").GetProxy("https", "https://rapid7.com")

I decided to create this PR, as I tried to use this code and found a fault in readme .

Testing

Below is the list of confirmations for the need for example code to be fixed.

Firstly: I ran the code myself

• I ran the example code, and here is the listing.

C:\Projects\PR-tests>cat test_for_PR1.go
package main
import (
    "fmt"
    "github.com/rapid7/go-get-proxied/proxy"
)
func main() {
    p := proxy.NewProvider("").Get("https", "https://rapid7.com")
    if p != nil {
        fmt.Printf("Found proxy: %s\n", p)
    }
}

C:\Projects\PR-tests>go run test_for_PR1.go
# command-line-arguments
.\test_for_PR1.go:7:32: proxy.NewProvider("").Get undefined (type proxy.Provider
 has no field or method Get)

C:\Projects\PR-tests>

• However, corrected code does work,

C:\Projects\PR-tests>cat test_for_PR2.go
package main
import (
    "fmt"
    "github.com/rapid7/go-get-proxied/proxy"
)
func main() {
    p := proxy.NewProvider("").GetProxy("https", "https://rapid7.com")
    if p != nil {
        fmt.Printf("Found proxy: %s\n", p)
    }
}

C:\Projects\PR-tests>go run test_for_PR2.go
Found proxy: WinHTTP:NamedProxy|://1.1.1.1:80

C:\Projects\PR-tests>

Secondly: I checked upstream code, and, there is type Provider interface, which does not define Get, but does define GetProxy,

go-get-proxied/proxy/provider.go

Line 40 in 7987917

GetProxy(protocol string, targetUrl string) Proxy

Thirdly: Third-party code also uses GetProxy(), for example, here: https://github.com/keyring-so/keyring-desktop/blob/9c6ca18257fee150f922d7559a85e7270373bcdc/app.go#L80

In light of these factors, I'm making this Push Request.