Fix context being ignored for some DNS requests

Author: rtpt-erikgeiser

options.go

@@ -130,11 +130,11 @@ func (opts *Options) WithDCTarget(ctx context.Context, protocol string) (*Creden
 
 	var dcAddr string
 
-	host, port, err := resolver.LookupFirstService(context.Background(), protocol, cred.Domain)
+	host, port, err := resolver.LookupFirstService(ctx, protocol, cred.Domain)
 	if err != nil {
 		lookupSRVErr := fmt.Errorf("could not lookup %q service of domain %q: %w", protocol, cred.Domain, err)
 
-		dcAddr, err = resolver.LookupDCByDomain(context.Background(), cred.Domain)
+		dcAddr, err = resolver.LookupDCByDomain(ctx, cred.Domain)
 		if err != nil {
 			return nil, nil, fmt.Errorf("could not find DC: %w and %w", lookupSRVErr, err)
 		}

resolver.go

@@ -59,7 +59,7 @@ func (r *resolver) LookupFirstService(ctx context.Context, protocol string, doma
 func (r *resolver) LookupDCByDomain(ctx context.Context, domain string) (string, error) {
 	// Unfortunately, Go does not implement SOA lookups, so we lookup the domain
 	// for DC IPs and reverse lookup their hostnames instead.
-	dcAddrs, err := r.LookupIP(context.Background(), "ip", domain)
+	dcAddrs, err := r.LookupIP(ctx, "ip", domain)
 	if err != nil {
 		return "", fmt.Errorf("lookup domain itself: %w", err)
 	}
@@ -70,7 +70,7 @@ func (r *resolver) LookupDCByDomain(ctx context.Context, domain string) (string,
 
 	dcAddr := dcAddrs[0].String()
 
-	names, err := r.LookupAddr(context.Background(), dcAddr)
+	names, err := r.LookupAddr(ctx, dcAddr)
 	if err == nil {
 		domain, names = splitResultsInDomainAndHostname(names, domain)