moved env to .env.example, update setup method

.env.example

@@ -0,0 +1,22 @@
+# set timezone to get correct log timestamp
+TZ=ETC/UTC
+
+# generate secret with `openssl rand -base64 32`
+GOPROXY_API_JWT_SECRET=
+
+# the JWT token time-to-live
+GOPROXY_API_JWT_TOKEN_TTL=1h
+
+# API/WebUI login credentials
+GOPROXY_API_USER=admin
+GOPROXY_API_PASSWORD=password
+
+# Proxy listening address
+GOPROXY_HTTP_ADDR=:80
+GOPROXY_HTTPS_ADDR=:443
+
+# API listening address
+GOPROXY_API_ADDR=127.0.0.1:8888
+
+# Debug mode
+GOPROXY_DEBUG=false