misc: Drop support for versions before Go 1.12

.travis.yml

@@ -1,12 +1,5 @@
 language: go
 go:
-- 1.5
-- 1.6
-- 1.7
-- 1.8
-- 1.9
-- "1.10"
-- 1.11
 - 1.12
 sudo: required
 addons:
@@ -18,9 +11,6 @@ cache:
   directories:
   - $HOME/.gimme
   - "$HOME/google-cloud-sdk/"
-env:
-  global:
-  - GO15VENDOREXPERIMENT=1
 install:
 - true
 script:

README.md

@@ -31,7 +31,9 @@ Windows in various formats of the
 
 ### Compile from source
 
-The only requirement for building tusd is [Go](http://golang.org/doc/install) 1.5 or newer.
+The only requirement for building tusd is [Go](http://golang.org/doc/install).
+Currently only Go 1.12 is tested and supported and in the future only the two latest
+major releases will be supported.
 If you meet this criteria, you can clone the git repository, install the remaining
 dependencies and build the binary: