golang sdk; how can I check horizon.Error.Problem

Question

package main

import (
    "log"

    "github.com/stellar/go/clients/horizonclient"
    "github.com/stellar/go/keypair"
)

//unfunded seed on testnet
var stellar_seed = "SANIUNNZFTU7LNMYXMWL25SAYEQE7GI2JLBG2DMSMA3DLNEBOPH7HAMI"

func main() {
    // Make a keypair for a known account from a secret seed
    kp, _ := keypair.Parse(stellar_seed)

    // Get the current state of the account from the network
    client := horizonclient.DefaultTestNetClient
    ar := horizonclient.AccountRequest{AccountID: kp.Address()}
    sourceAccount, err := client.AccountDetail(ar)
    if err != nil {
        // log.Println(horizon.Error.Problem)
        log.Fatalln(err)
    }
    log.Println(sourceAccount)
}

Running this, I get the message:

2022/02/25 23:41:29 horizon error: "Resource Missing" - check horizon.Error.Problem for more information
exit status 1

How do I "check horizon.Error.Problem"?

Answer 1

"george" from the "Stellar Developers" discord #horizon chat answered me:

you can use the horizonclient.GetError(err) helper to retrieve the Problem structure and inspect it. For example,

if err != nil {
    log.Println(err)
    if p := horizonclient.GetError(err); p != nil {
        fmt.Printf("  Info: %s\n", p.Problem)
        if results, ok := p.Problem.Extras["result_codes"]; ok {
            fmt.Printf("  Extras: %s\n", results)
        }
    }
}