code: func (g *Cloud) SetProxyForGlobalForwardingRule(forwardingRuleName, targetProxyLink string) error {
  	ctx, cancel := cloud.ContextWithCallTimeout()
  	defer cancel()
  
  	mc := newForwardingRuleMetricContext("set_proxy", "")
  	target := &compute.TargetReference{Target: targetProxyLink}
  	return mc.Observe(g.c.GlobalForwardingRules().SetTarget(ctx, meta.GlobalKey(forwardingRuleName), target))
  }
docs: // SetProxyForGlobalForwardingRule links the given TargetHttp(s)Proxy with the given GlobalForwardingRule.
  // targetProxyLink is the SelfLink of a TargetHttp(s)Proxy.