Implement runners execute route

Co-authored-by: Tobias Kantusch <tobias.kantusch@student.hpi.uni-potsdam.de>

runner/runner.go

@@ -1,6 +1,7 @@
 package runner
 
 import (
+	"context"
 	"encoding/json"
 	"sync"
 )
@@ -12,6 +13,9 @@ const (
 	StatusRunning  Status = "running"
 	StatusTimeout  Status = "timeout"
 	StatusFinished Status = "finished"
+
+	// runnerContextKey is the key used to store runners in context.Context
+	runnerContextKey = "runner"
 )
 
 type Runner interface {
@@ -69,3 +73,12 @@ func (r *ExerciseRunner) Status() Status {
 func (r *ExerciseRunner) Id() string {
 	return r.id
 }
+
+func NewContext(ctx context.Context, runner *Runner) context.Context {
+	return context.WithValue(ctx, runnerContextKey, runner)
+}
+
+func FromContext(ctx context.Context) (*Runner, bool) {
+	runner, ok := ctx.Value(runnerContextKey).(*Runner)
+	return runner, ok
+}