Restructure project

We previously didn't really had any structure in our project apart
from creating a new folder for each package in our project root.
Now that we have accumulated some packages, we use the well-known
Golang project layout in order to clearly communicate our intent
with packages. See https://github.com/golang-standards/project-layout

internal/runner/inactivity_timer_mock.go

@@ -0,0 +1,43 @@
+// Code generated by mockery v0.0.0-dev. DO NOT EDIT.
+
+package runner
+
+import (
+	time "time"
+
+	mock "github.com/stretchr/testify/mock"
+)
+
+// InactivityTimerMock is an autogenerated mock type for the InactivityTimer type
+type InactivityTimerMock struct {
+	mock.Mock
+}
+
+// ResetTimeout provides a mock function with given fields:
+func (_m *InactivityTimerMock) ResetTimeout() {
+	_m.Called()
+}
+
+// SetupTimeout provides a mock function with given fields: duration
+func (_m *InactivityTimerMock) SetupTimeout(duration time.Duration) {
+	_m.Called(duration)
+}
+
+// StopTimeout provides a mock function with given fields:
+func (_m *InactivityTimerMock) StopTimeout() {
+	_m.Called()
+}
+
+// TimeoutPassed provides a mock function with given fields:
+func (_m *InactivityTimerMock) TimeoutPassed() bool {
+	ret := _m.Called()
+
+	var r0 bool
+	if rf, ok := ret.Get(0).(func() bool); ok {
+		r0 = rf()
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	return r0
+}