time.clock was removed in Python 3.8

[tirkarthi]

etcd3gw/tests/test_etcd3gw.py
347:        lock = self.client.lock(id='xyz-%s' % time.clock(), ttl=60)

etcd3gw/examples/etcd.py
57:    lock = Lock('xyz-%s' % time.clock(), ttl=10000, client=client)

Ref : https://github.com/python/cpython/pull/13270

[dims]

@tirkarthi could you help fix this with a PR?

[tirkarthi]

I have raised #36 . I feel time.perf_counter to be more appropriate choice.