maint: drop go 14, 15, 16 (#225)

## Which problem is this PR solving?

- 16 has been eol since march 2022
- catalyst is [upgrading
testify](#224), which no
longer works with those older versions

.circleci/config.yml

@@ -17,7 +17,7 @@ filters_publish: &filters_publish
 matrix_goversions: &matrix_goversions
   matrix:
     parameters:
-      goversion: ["14", "15", "16", "17", "18", "19", "20"]
+      goversion: ["17", "18", "19", "20"]
 
 # Default version of Go to use for Go steps
 default_goversion: &default_goversion "20"

README.md

@@ -12,7 +12,7 @@ For tracing support and automatic instrumentation of Gorilla, `httprouter`, `sql
 
 ## Dependencies
 
-Golang 1.14+
+Golang 1.17+
 
 ## Contributions