fix: add post request headers only if auth request method is post #85

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	12m 16s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	29m 47s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	30m 52s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	21m 24s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	21m 39s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	14m 54s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	30m 16s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	31m 2s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	22m 42s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	23m 1s
	3h 57m 53s

Provide feedback