After Diploma in Mechanical Engineering you can obviously go for government jobs for the post of Junior Engineer or Technician in different organization of government.

There is an exam called SSC JE which offers jobs in various departments for the Junior Engineer. Apart from this if you are interested in Railways then RRB JE is a exam which you can apply for to be a junior engineer. This jobs have very good salaries and a respectable post after your Diploma. Now research institutes like ISRO, DRDO etc recruits Diploma engineers as technicians and you can get the notification for this exams in the career section of official website.

To know more about SSC JE visit the link below:

https://competition.careers360.com/exams/ssc-je#:~:text=About%20SSC%20JE%202021&text=SSC%20JE%20is%20conducted%20to,candidates%20for%20the%20recruitment%20process.

To know more about RRB JE visit the link below:

https://competition.careers360.com/exams/rrb-je-recruitment

I hope this answer helps. All the very best for your future endeavors!