feat: rewrite all the examples for using env params and get rid of the mysql-client initial function

.gitignore

@@ -22,3 +22,7 @@ stylesheet.css
 
 # jenv local settings
 .java-version
+
+# environment shell script
+
+env.sh

env.sh.example

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+export TIDB_HOST='xxxxxxxx.aws.tidbcloud.com'
+export TIDB_PORT='4000'
+export TIDB_USER='xxxxxxxxxxx.root'
+export TIDB_PASSWORD='xxxxxxx'
+export TIDB_DB_NAME='test'
+export USE_SSL='true'
+
+jdbc_url="jdbc:mysql://${TIDB_HOST}:${TIDB_PORT}/${TIDB_DB_NAME}"
+if [ 'true'=="${USE_SSL}" ]; then
+  jdbc_url="${jdbc_url}?sslMode=VERIFY_IDENTITY&enabledTLSProtocols=TLSv1.2,TLSv1.3"
+fi
+
+export TIDB_JDBC_URL=${jdbc_url}