jwoos/rainbowgif: quantize.go; 16 LoC

Found a possible issue in [jwoos/rainbowgif](https://www.github.com/jwoos/rainbowgif) at [quantize.go](https://github.com/jwoos/rainbowgif/blob/f55fd45f6c1a90ad9f00088e289915c0ac5abe3a/quantize.go#L53-L68)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> reference to c was used in a composite literal at line 60

[Click here to see the code in its original context.](https://github.com/jwoos/rainbowgif/blob/f55fd45f6c1a90ad9f00088e289915c0ac5abe3a/quantize.go#L53-L68)

Click here to show the 16 line(s) of Go which triggered the analyzer.

```go
for i, c := range colors {
colorInfo, okay := palette[c]
if !okay {
colorInfo = struct {
addr *color.RGBA
index int
}{
addr: &c,
index: len(paletteSlice),
}
palette[c] = colorInfo
paletteSlice = append(paletteSlice, colorInfo.addr)
}

indexMapping[i] = colorInfo.index
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: f55fd45f6c1a90ad9f00088e289915c0ac5abe3a

Open quantize.go at lines 53-68 in the linked rainbowgif commit and read the surrounding range-loop code first. Decide whether the reported reference to c is a bug, mitigated, or desirable behavior, then record the corresponding reaction on this issue; completion is a single classification reaction.

Written by the indexing model from the issue text.