Our little one didnt like a leash either. So while we were inside we kept his harness on him then after awhile we would attach the leash to him and constantly take him everywhere with us in the house.. even while i was sitting at the computer i had him on a leash for awhile.
he got used to it real fast
He is only 5 months old! now once his harness goes on he knows the leash is next so he just sits and waits