travis: bump Go versions to 1.15/1.16 and build distro to bionic

Let's join the 21st century.

Signed-off-by: Dan Williams <[email protected]>

Author: dcbw

.travis.yml

@@ -1,11 +1,9 @@
 language: go
-dist: trusty
+dist: bionic
 
 go:
-  - 1.9.x
-  - 1.10.x
-  - 1.11.x
-  - 1.12.x
+  - 1.15.x
+  - 1.16.x
 
 env:
   matrix:
@@ -18,19 +16,9 @@ env:
 matrix:
   fast_finish: true
 
-# Ubuntu 14.04 (trusty) doesn't have a new enough util-linux for nsenter,
-# so we have to build it ourselves.
 before_install:
- - wget https://www.kernel.org/pub/linux/utils/util-linux/v2.24/util-linux-2.24.1.tar.gz -qO - | tar -xz -C .
  - sudo apt-get update
  - sudo apt-get install -y libncurses5-dev libslang2-dev gettext zlib1g-dev libselinux1-dev debhelper lsb-release pkg-config po-debconf autoconf automake autopoint libtool
- - pushd util-linux-2.24.1
- -   ./autogen.sh
- -   ./configure
- -   make
- -   sudo cp ./nsenter /usr/bin
- - popd
- - rm -rf util-linux-2.24.1
 
 install:
  - go get golang.org/x/tools/cmd/cover