How do i make a player faster when a key is pressed?

I'm trying to make the player go faster and play an animation while a certain key is being pressed but nothings working.

this is the code I put in the starter pack so far:

local playr = game.Players.LocalPlayer
local mouse = playr:GetMouse()
local uis = game:GetService("UserInputService")

local character = playr.CharacterAdded:wait(0.1)
character:WaitForChild("Humanoid")
character.Humanoid.WalkSpeed = "50"
local animationTrack = playr.Character.Humanoid:LoadAnimation(animation)

function run(key,gp)
    if key.KeyCode == Enum.KeyCode.Q and gp == false then 
        script.Fwoosh:Play()
        game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = "250"
    end
end

uis.InputBegan:connect(run)

function dont(key)
    if key.KeyCode == Enum.KeyCode.Q and gp == false then
        game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = "50" 
    end
end

uis.InputEnded:connect(dont)

doesnt work :(

The error is that you are using “250” instead of 250, the walk speed cannot be a string, but not only that, you are not specifying the key when they press, so any key will make the player sprint, but you need to specify an input function for user input service otherwise the script will never know the key they clicked

local playr = game.Players.LocalPlayer
local mouse = playr:GetMouse()
local uis = game:GetService("UserInputService")
local character = playr.CharacterAdded:Wait() -- Remove :wait(0.1)
character:WaitForChild("Humanoid")
character.Humanoid.WalkSpeed = 50 -- Use Numbers
local animationTrack = playr.Character.Humanoid:LoadAnimation(animation)

function run(key,gp)
    if key.KeyCode == Enum.KeyCode.Q and not gp then 
        script.Fwoosh:Play()
        game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 250
    end
end

function stop()
    game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 50
end

uis.InputBegan:connect(
    function(input)
        if input.KeyCode == Enum.KeyCode.Q then
            run(Q) -- you have to tell the script the key the player clicked
        end
    end
    uis.InputEnded:connect(
        stop() --no point of the key parameter since they will let go of the key
    )
)

Answer

Well, first, you can put in StarterPlayer considering it always updates your position even when the position is modified by a LocalScript. So something like this may work:

local uis = game:GetService("UserInputService")
local character = workspace:WaitForChild(script.Parent.Parent.Name)
local sprinting = false

--Camera options
local EasingSpeed = 3
local sprintFOV = 120
local defaultFOV = 70

--Speed options
local defaultRunSpeed = 16
local sprintRunSpeed = 32

--Jump options (optional)
local highJump = true
local defaultJumpPower = 50
local sprintJumpPower = 75

uis.InputBegan:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		sprinting = true
	end
end)

uis.InputEnded:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		sprinting = false
	end
end)


while wait() do
	if sprinting == true then
		if workspace.CurrentCamera.FieldOfView < sprintFOV + 1 then
			workspace.CurrentCamera.FieldOfView = workspace.CurrentCamera.FieldOfView + EasingSpeed
		end
		character.Humanoid.WalkSpeed = sprintRunSpeed
		if highJump == true then
			character.Humanoid.JumpPower = sprintJumpPower
		end
	elseif sprinting == false then
		if workspace.CurrentCamera.FieldOfView > defaultFOV - 1 then
			workspace.CurrentCamera.FieldOfView = workspace.CurrentCamera.FieldOfView - EasingSpeed
		end
		character.Humanoid.WalkSpeed = defaultRunSpeed
		character.Humanoid.JumpPower = defaultJumpPower
	end
end

If you need some things explained, continue to the next part.

Explanation So, if you look at the script, you can see many variables at the top. What these really mean is simple: EasingSpeed = The amount of FOV (Field of View) it changes every tick when sprinting sprintFOV = The FOV that is eased to when sprinting defaultFOV = The default FOV (FOV when not sprinting) defaultRunSpeed = The Humanoids WalkSpeed when not sprinting sprintingRunSpeed = The Humanoids WalkSpeed when sprinting highJump = whether or not the Humanoids JumpPower is affected by sprinting defaultJumpPower = the Humanoids JumpPower when not sprinting sprintingJumpPower = the Humanoids JumpPower when sprinting Feel free to customize these how you wish!

flunkywhat, Game Dev