Add Go 1.18 support

[Aoang]

No description provided.

[Aoang]

Results:


[/home/runner/work/fasthttp/fasthttp/server.go:1776] - G402 (CWE-295): TLS MinVersion too low. (Confidence: HIGH, Severity: HIGH)
    1775: 	if s.TLSConfig == nil {
  > 1776: 		s.TLSConfig = &tls.Config{}
    1777: 	}



[/home/runner/work/fasthttp/fasthttp/examples/letsencrypt/letsencryptserver.go:23-28] - G402 (CWE-295): TLS MinVersion too low. (Confidence: HIGH, Severity: HIGH)
    22: 
  > 23: 	cfg := &tls.Config{
  > 24: 		GetCertificate: m.GetCertificate,
  > 25: 		NextProtos: []string{
  > 26: 			"http/1.1", acme.ALPNProto,
  > 27: 		},
  > 28: 	}
    29: 



[/home/runner/work/fasthttp/fasthttp/client.go:1898] - G402 (CWE-295): TLS MinVersion too low. (Confidence: HIGH, Severity: HIGH)
    1897: 	if c == nil {
  > 1898: 		c = &tls.Config{}
    1899: 	} else {

This pull request should not handle this https://github.com/valyala/fasthttp/runs/5595807170?check_suite_focus=true

[Aoang]

TBR

[erikdubbelboer]

Thanks!