[ Feature ]
Refactor lagacy code by

• new design pattern
• multisession for mgo each request: this practice will solve EOF issue and performance.

[ Detail ]

• clean and nice semantic code.
• use session copy method instead session pointer for pass by ref each request.

url :
save session in mgo golang : https://stackoverflow.com/questions/39634610/save-session-in-mongodb-golang
example mgo best practice : https://gist.github.com/345161974/4f2048f90584a64891cf07997bfd9e23
issue session close: https://stackoverflow.com/questions/52849583/how-can-i-know-if-a-mgo-session-is-closed
EOF after subsequent req: https://stackoverflow.com/questions/30086489/go-lang-and-labix-mgo-getting-eof-after-subsequent-requests
handle EOF : https://stackoverflow.com/questions/52514636/how-to-handle-eof-error-from-mgo-in-golang
maintain mgo session : https://stackoverflow.com/questions/26574594/best-practice-to-maintain-a-mgo-session
handle disconnect mongo : https://groups.google.com/g/mgo-users/c/XM0rc6p-V-8