Upgrade to Go 1.13

.travis.yml

@@ -7,6 +7,7 @@ os:
 
 go:
   - "1.12.x"
+  - "1.13.x"
 
 before_script:
 - go get -u 

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.12
+FROM golang:1.13
 
 RUN apt-get update
 RUN apt-get install bash make git curl jq -y

docs/misc/technical-details.md

@@ -1,6 +1,6 @@
 # A few technical details...
 
-The ABS interpreter is built with Golang version `1.11`, and is mostly based on [the interpreter book](https://interpreterbook.com/) written by [Thorsten Ball](https://twitter.com/thorstenball).
+The ABS interpreter is built with Golang version `1.13`, and is mostly based on [the interpreter book](https://interpreterbook.com/) written by [Thorsten Ball](https://twitter.com/thorstenball).
 
 ABS is extremely different from Monkey, the "fictional" language the reader builds throughout the book, but the base structure (lexer, parser, evaluator) are still very much based on Thorsten's work.
 

evaluator/evaluator_test.go

@@ -802,7 +802,7 @@ func TestBuiltinFunctions(t *testing.T) {
 		{`find([1,2,3,3], f(x) {x == 3})`, 3},
 		{`find([1,2], f(x) {x == "some"})`, nil},
 		{`arg("o")`, "argument 0 to arg(...) is not supported (got: o, allowed: NUMBER)"},
-		{`arg(3)`, ""},
+		{`arg(99)`, ""},
 		{`pwd().split("").reverse().slice(0, 33).reverse().join("").replace("\\", "/", -1).suffix("/evaluator")`, true}, // Little trick to get travis to run this test, as the base path is not /go/src/
 		{`cwd = cd(); cwd == pwd()`, true},
 		{`cwd = cd("path/to/nowhere"); cwd == pwd()`, false},