Day 1 part 1

.gitignore

@@ -1,2 +1,3 @@
 .idea
-
+inputs
+test_inputs

main.go

@@ -1,7 +1,42 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const DIR = "/home/fernando/GolandProjects/advent-20/"
+
+func readInput(isTest bool) string {
+	bytes, err := os.ReadFile(DIR + "inputs/01.txt")
+	if err != nil {
+		fmt.Println(err)
+		panic("Error reading file.")
+	}
+
+	return string(bytes)
+}
 
 func main() {
-	fmt.Println("Hello, World!")
+	input := readInput(false)
+	values := strings.Split(input, "\n")
+	remainders := make(map[int]bool)
+
+	for _, valueStr := range values {
+		value, ok := strconv.Atoi(valueStr)
+		if ok != nil {
+			panic("Error converting to int")
+		}
+
+		currentRemainder := 2020 - value
+
+		if _, ok := remainders[currentRemainder]; ok {
+			fmt.Println(value * currentRemainder)
+			break
+		} else {
+			remainders[value] = true
+		}
+	}
 }