unity do something while holding code example

Example: How to hold key down unity

// If Key Is Held Down
Input.GetKey("Key")

// If Key Is Held Down With if Statement
if (Input.GetKey("Key"))
{
    // Whatever is in this will get called when "Key" is held down
}

// Example 
if (Input.GetKey("left shift"))
{
    RunBool = true;
    WalkBool = false;
}