Rocket controller for a Unity game
UPDATE: Unity has built-in support for rebindable keys. I still urge you to setup rebindable keys, but a better way to do so would be through the system described by https://codereview.stackexchange.com/a/85568/35495. 

One thing I really see happening with your code is that some poor gamer using a non-qwerty keyboard (like azerty or dvorak) will have an unplayable game because their keyboard has a different layout. for example, as an azerty-player I use ZQSD instead of WASD, and the W key is on the bottom line. In addition, there are players that use ESDF so they have a larger keyspace available for hotkeys.

The usual way of handling this is:

Make a .cfg or .ini file (basically a text file) in a config folder in your game

Put this code in there:

[Input]
button_W = forward;
button_S = back;
button_A = left;
button_D = right;
//any other buttons you need;


Then you load this into a dictionary when the game loads using a text file parser (plenty of examples for that online).

When the user then does any input, you check which button they pushed. Is it one of the configured buttons? then do the corresponding action. Is it a non-configured button? then return.

You can then use the default Unity launcher to configure these buttons, or you can configure these buttons using a custom config menu ingame.