You make a number of very large unexamined assumptions three of which are most relevant to your question:
a) that freewill exists,
b) that given freewill, it could not be exercised in the absence of evil.
c) that there must be evil to recognize good.
We can dispense with "b" and "c" very quickly.
However, "a" is a complicated issue.
If we assume that your god gave us freewill and did not allow evil to exist, it would still be possible for us to use our freewill in making choices among a multiplicity of good "things" and good, better, and best "things."
If you are going to argue "c," that we would not know what is good without evil, i.e., pain, suffering, etc., to compare it with, we make many "freewill" choices without giving any thought to the state of the goodness or evilness of the "things" we choose, as in the case cited immediately above.
Consider also, all those creatures in the world who are born experiencing the evil of pain and, then, died without ever having experienced or been introduced to the concept of good.
Moreover, if God felt we needed the comparison, a one shot bit of pain and suffering, like a pin prick on the finger, instead of wars, diseases, crime, etc., would have done the trick.
Better still, since He is All-Powerful, and since it is quite easy to describe evil events without their occurrence, He could have given us the knowledge of the difference between good and evil without our having to experience any of the latter.
Enough of this; let's move on to your assumption, "a," that your god gave us freewill.
The real issue is whether there is such a mental state as "freewill, i.e., INDETERMINISM."
Or, is EVERYTHING in the universe caused, i.e., DETERMINED?
If you are interested, the definition of FREEWILL, i.e., indeterminism, for those who believe in it is: "an effect withOUT an antecedent cause," a definition which will be amended later.
For determinism: "an effect WITH an antecedent cause."
Let us assume that your god gave us freewill.
Now you must face a few other facts.
Your god created the laws of the universe, also, under which everything is governed.
How your brain, a physical substance, functions, i.e., your mind, is controlled by His laws.
Moreover, Your god is All-Knowing.
He knew long before he created the universe, and its laws, and after "time was created," "quadrillion zillions" of years before you were born, every act you would perform and every thought you would think, good or bad.
You do not have the freedom to do other than what He knows, being omniscient, you will do according to His laws that control everything in the universe.
I'm going to quote some passages that are pertinent to this issue, from my book, Hey! IS That You, God?.
"God" and "Schievella" are arguing; for convenience, however, I shall choose only relevant statements.
God: Everybody knows that man has free will.
Schievella: Even I might agree to that. . . . Nevertheless, free will is possible only as SOME FORM OF DETERMINISM. There is always a reason, a cause, for any choice we make even if it is only the [Your] law-controlled neuronal activity of the brain without which there would be no choice. . . . A pianist's creative musical flight of freedom would not be possible were it not for his neuronal activity and the years of disciplined practice and forming of habits of wrist and finger movements. The same applies to thinking. Freedom of thought comes out of a background of mental, educational, [nurtured], and academic preparation. Thoughts and choices do not occur in a vacuum any more than the progress of one age is possible without the progress of a previous age.   Nor does a painter without paints, brushes, canvas, whatever, and neurons in his brain, make [free] choices about how to paint a portrait. There is always some form of cause and effect. And if You created us, then You are a cause of our actions. Even the concept of a god can be a cause just as a concept of Santa Claus causes children to behave in a certain way. . . . If You did give us free will, You have no right to punish us if we choose bad over good. You created all events in the universe as well as the possibility of all events, physical and moral. If we choose bad, You made us capable of doing it. . . . You know when we will choose evil. So, if You don't stop us, as a good parent ought to, then you are twice guilty of not preventing evil, as You expect us to do. Therefore, You are an accomplice just as when You, and Your Satanic personality, connived to ruin Job. After all, if our parents are evil for letting us do bad, why aren't You?
Having said all this, let's consider further this other concept of freewill which has nothing to do with whether there is a god or not.
Such a concept is related to larger issues such as:
The distinction between those acts we "WILLINGLY" perform and those we do not.
What is a person?
What is mind?
is the meaning
we attribute to the term, 'choice'?
What does it mean, then, to say "freewill is a form of determinism.?
Now the issue becomes more complex.
When a tree dies and falls in the forest, there is no choice on the part of the tree to do that.
It is a strict deterministic effect of the trees inability to withstand whatever killed it and for its rotted roots to resist the weather conditions that felled it.
It is analogous to a person's inability to stay alive when he is stricken by certain diseases that medical science cannot yet cure or when he reaches a certain age that science has not yet learned to extend.
As a human being, I make choices.
I (depending on how you define the term, 'I' ) also make conditioned responses (I COULD NOT have made a different response given the circumstances at hand.) many of which I am often not aware I'm performing .
Often I make deliberate choices (choosing one action out of a number of possible actions.
On what basis do I make one choice instead of another?
For the moment, we must digress.
What do I mean by the term, 'I'?
"I" is the PERSON that I am.
I do not mean merely that I look like a human being, that I have two brown eyes, a nose  two arms a torso, and two legs, etc.
If, because of some accident, I was unfortunate enough to lose my eyes, arms, nose, legs, etc., I'd still be a person.
As a person "I" am a complex of my particular physical characteristics and MORE IMPORTANTLY my history of experiences.
It is those things that distinguish one "identical" twin from another.
In other words, a person's mind is a complex of functions, neuronal states and activity, and his history of "stored" experiences, remembered, forgotten (possibly sub-conscious), induced by parental, nurtured, ethical, moral, spiritual, educational, physical, cultural, social, diseased, damaged, aesthetic, genetic, whatever, input and "housed" in a physical brain.
All or some of those experiences weigh in the making of a choice.
Were there no sense faculties acquiring that history of experiences and no living physical brain "housing" that history of experiences, no choice could be made.
The strongest, more compelling complex, "tug of war," of that input, neuronal states, and functions DETERMINE the "free" choice made.