Implementing this functionality would would allow you to do things like calculate the mean difference between two distributions:
using Statistics
xs = rand(1000)
ys = rand(1000)
bootstrap((x,y)->mean(x)-mean(y), (xs, ys), BasicSampling(1000)) # mock API
Which would be equivalent(ish) to the following (minus the nice extras that Bootstrap.jl provides):
using Statistics, StatsBase
map(_->mean(sample(xs, size(xs)))-mean(sample(ys, size(ys))), 1:1000)