add the forward euler method in golang (#485)

* add the forward euler method in golang * change the name golang to go

Author: Julian

contents/forward_euler_method/code/golang/euler.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+"fmt"
+"math"
+)
+
+func forwardEuler(timeStep float64, n int) []float64 {
+result := make([]float64, n)
+result[0] = 1
+for x := 1; x < n; x++ {
+result[x] = result[x-1] - 3*result[x-1]*timeStep
+}
+return result
+}
+
+func check(result []float64, threshold, timeStep float64) bool {
+approx := true
+for x := 0.; int(x) < len(result); x++ {
+solution := math.Exp(-3. * x * timeStep)
+if math.Abs(result[int(x)]-solution) > threshold {
+fmt.Println(result[int(x)], solution)
+approx = false
+}
+}
+return approx
+}
+
+func main() {
+timeStep, threshold := .01, .01
+n := 100
+
+result := forwardEuler(timeStep, n)
+if check(result, threshold, timeStep) {
+fmt.Println("All values within threshold")
+} else {
+fmt.Println("Value(s) not within threshold")
+}
+}

contents/forward_euler_method/forward_euler_method.md

@@ -123,6 +123,8 @@ Full code for the visualization follows:
 [import, lang:"swift"](code/swift/euler.swift)
 {% sample lang="f90" %}
 [import, lang:"fortran"](code/fortran/euler.f90)
+{% sample lang="go" %}
+[import, lang:"go"](code/golang/euler.go)
 {% endmethod %}
 
 <script>