function dijkstra!(graph,start)
# We start by initializing all nodes.
initialize_single_source!(graph, start)
# Then, we put all nodes in a priority queue, based on the risk of the node.
queue = PriorityQueue(u=>u.risk for u in graph)
# We look at each node in the queue.
while !isempty(queue)
u = dequeue!(queue)
# For each neighbour of a node,
# we try to update the risk of that neighbour.
for (v,cost) in u.neighbours
relax!(u,v, cost)
# if the neighbour exists in the queue,
# we update the priority of that node with it's (possibly) new risk.
# NOTE: If we do not incorporate the if-statement,
# we create an infinite loop if there is a cycle in the graph.
if haskey(queue,v) queue[v] = v.risk end
end
end
end