recommend changing -useIndex flag to -use-index to match other flags
fmt.Print("\r") after ^C should probably print to stderr instead of stdout
typo UseIndx in comment
seems weird to see stderr as the name of a logger -- how about log or lgr?
getIndexLocators() and doIndexReads() - instead of putting the entire func in an if ctx.Err()==nil, just put if ctx.Err() != nil { return } at the top and un-indent the rest
Similarly you could do for i := 0; i < *Repeat && ctx.Err() == nil; i++ { in main()
At the end of main, maybe it's better not to skip the summary when ctx.Err()!=nil, i.e., exiting on a signal?
Having two copies of doIndexReads/doReads doesn't seem ideal. Maybe something like this could handle both cases, and the caller would just provide a nil indexLocatorChan if !*UseIndex?
for ctx.Err() == nil {
var locator string
if indexLocatorChan != nil {
select {
case locator = <- indexLocatorChan:
case <-ctx.Done():
return
}
} else {
locator = nextLocator.Load().(string)
}
// ...
Is it worth deduplicating the keepstore index results, to improve cache-avoidance a bit?
Updated by 
Updated by