Add day 2 solution.

2018/internal/util/input.go

@@ -0,0 +1,24 @@
+package util
+
+import (
+	"bufio"
+	"os"
+)
+
+// ReadInput isn't here to make friends. It is highly specific to this domain.
+// It assumes the first argument on the command-line is a file with input. It
+// returns an array of strings containing the lines of that file.
+func ReadInput() []string {
+	file, err := os.Open(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+
+	lines := []string{}
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		lines = append(lines, scanner.Text())
+	}
+
+	return lines
+}