Four algorithms to find the Nth Fibonacci number
For tailHelper(), the term == 1 case is superfluous and should be eliminated.

In fibonacciBinet(), the quantity \$\frac{1 + \sqrt{5}}{2}\$ appears twice.  Since that quantity is known as the Golden Ratio, I would define an intermediate value

var phi = (1 + math.Sqrt(5)) / 2;


However, none of these four solutions is particularly idiomatic for Go.  The most expressive way to write a Fibonacci sequence in Go is as an iterator, such as this one.