As other people mentioned, you can also use GraphMakie.jl
Bucheim breaks with your graph because it assumes double edges and a node cannot have multiple parent nodes.
If this is not a deal breaker you can work it around with SimpleWeightedDiGraph:
using GraphMakie
g = SimpleWeightedDiGraph(5)
add_edge!(g, 1, 2, 0.5)
add_edge!(g, 1, 3, 2.0)
add_edge!(g, 1, 4, 3.5)
add_edge!(g, 1, 5, 5.0)
edws = [get_weight(g, e.src, e.dst) for e in edges(g)]
graphplot(g, layout=NetworkLayout.Buchheim(), edge_width=edws, arrow_size=5 .+ 5 .* edws)
