New Features

• Implement Server.start_serving() and related APIs.
  (by @jlaine in 7a4f00a)

• Make Server an asynchronous context manager.
  (by @jlaine in d6c67e7 for #221)

Performance

• Start using high-performance uv_udp_t handle. This
  should result in a significantly faster UDP support.
  (by @1st1 in c2b65bc)

• Make address validation faster in udp.sendto().
  (by @1st1 in 46c5e9e)

Misc

• OSError is no longer logged by Transports.
  This matches asyncio behaviour in 3.8.
  (by @Tobotimus in ef29dab)

Build

• Upgrade to libuv v1.31.0.
  (by @1st1 in c2b65bc and 1fad621)

• Use manylinux-2010. This means we no longer provide
  32bit builds for Linux.
  (by @1st1 in 3174b7d)

Bug Fixes

• Fix circular references in SSL implementation to reduce
  the need for GC.
  (by @fantix in 3070ec8)

• Fix a memory leak in call_later() and call_at().
  The leak occurred when a callback argument had a reference to
  the event loop.
  (by @1st1 in 1a5dbc2 for #239)

• Fix compilation warnings.
  (by @JelleZijlstra in d9a111b)

• Round (instead of flooring) delay in call_later().
  This ensures that the callback is never called slightly before
  the specified time.
  (by @fantix in 8f037a6 for #233)

Bug Fixes

• Fix a circular references case in SSL implementation.
  (by @fantix in a2e0dd8 for #220)

• Cleanup references to callbacks in canceled callback handles.

  This removes potential reference cycles between bound methods
  and cancelled Handle / TimerHandle objects.

  (by @1st1 in f0a945d)

New Features

• New SSL implementation. The new implementation is faster and
  and more complete, and might become the default SSL implementation
  in asyncio 3.9.

  See the linked issue for more details.

  (by @fantix in 9cba749 for #158, #176)

• New uvloop.install() helper function.

  Instead of

  import asyncio
  import uvloop
  asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())

  it is now possible to simply write

  import uvloop
  uvloop.install()

  (by @1st1 in a3d8d40)

Bug Fixes

• All bug fixes from 0.11.0—0.11.3 are included in
  this release.

• ssl.CertificateError is no longer logged as it's delivered to
  the Protocol.connection_lost() anyways.
  (by @fantix in 848e478 for #195, #199)

• Don't use non-existent UDPTransport._address attribute.
  (by @jlaine in f24c2c5 for #207)

Performance

• Improve UDPTransport.sendto() performance.
  (by @jlaine in d5ad2b8 for #214)

Build

• Upgrade Cython 0.28.x -> 0.29.0.

• Upgrade libuv v1.22.0 -> v1.23.0.

Bug Fixes

• Use new PyOS_BeforeFork and PyOS_AfterFork_* 3.7 APIs when available
  (by @1st1 in 75e7c32)

• Fix async generators finalization to function correctly in debug mode
  (by @1st1 in dcbb1f4 for #200)

• Pass backlog to loop.create_unix_server() when a server is created via
  loop.create_server(sock=unix_sock, backlog=backlog).
  (by @hikoz in 40ad257)

• Don't raise "requires a DNS lookup" error on Unix Domain Socket (#204)
  (by @pax0r in 9fc3ca2 for #204)

• Fix use of PyContext* APIs in 3.7.1
  (by @1st1 in 7474800)

Build

• Bump Cython to 0.28.5
  (by @1st1 in 1bbd6a8)