Another Option:
Take Airport Metro Line from New Delhi Railway Station till Dhaula Kuan Metro Station. Take Auto from Dhaula Kuan to Delhi Cantt Railway Station.
Though 3 Km longer than 5Km distance of Delhi Cantt Metro Station and Tilak Nagar Metro Station.
Saving a lot of time due to Limited Stoppages and Direct Connection. No need to interchange like other lines.